What octane to run on 4.6 GT Anyway?

holler · Mar 2, 2004

lots of misconceptions about Ethanol

ethanol 101:

http://www.ethanolrfa.org/factfic_enperf.html

strongmad · Mar 3, 2004

The guys who say stick with 87 are right. Unless your car is tuned for higher octane gas or you have bumped the timing, you don't need to run premium. If you want to waste your money just because you think a sports car deserves something that says "premium" then go for it.

laser01gt · Jun 1, 2004

I always thought that higher octane meant higher horsepower. However by my own accidentle experiment i proved this to be a myth. My bone stock 2001 never chirped the tire in third with 91 octane. Then one time I filled up with 87 because I was gonna run on the freeway and to my suprise it chirped going into third!! This was about 2 months ago and I have be able to repeat my feat since.

cronin49 · Jun 1, 2004

FallenPhoenix said:
There's less actual fuel to burn the higher the octane rating, so the lowest you can go without pinging is best. If you do get a little knock you'll pick up some power with higher octane just by preventing detonation.

wrong.

snoopy98 · Jun 1, 2004

my car pings when i run 89 so i use 93 all the time forget what you all say i guess i will continue wasteing my money.

geegee · Jun 1, 2004

White Stang said:
I always use 91

Let's see! 18,000 miles a year / 18 mpg fuel mileage = 1000 gallons per year.

1000 g/y * $0.10 per gallon difference in prices for 91 = $100.

In addition you got worse gas mileage since lower octane fuel burns more efficiently...Okay, you just burned up $100 for nothing! And you're doing it each year.

Skud · Jun 1, 2004

Now I'm not arguing the fact that you should run the lowest octane possible, but my stang pings when I run 87. It'll only do it on a warm day and when I'm in stop and go traffic. I'll let out the clutch and start to take off in first; the RPM's drop to around 500. When I give it a bit of gas to get going, you can hear it ping.

One of the gas stations here sells 90 grade ethanol-blended fuel for the same price as 87 regular. When I run the 90 I get no pinging at all. I also get much better mileage with the 90 grade.

So, that would mean either my timing is bumped up (doubtful, since it's still stock) or what else? Plugs? Just crappy 87?

Riley

FallenPhoenix · Jun 1, 2004

cronin49 said:
wrong.

got anything to back that up? There are less fuel atoms to burn because that volume is taken up by the actual octane that's in the fuel. Less atoms per given volume of fuel = less power. If you care to back up your "wrong" then I'll be the first to admit I'm wrong.

ShadowGT · Jun 1, 2004

87, 89 or 91-93 all run about the same in my GT...actually it runs best with 89 or 87.

My wife's '00 V6 Stang pings badly with anything under 89. Only mods are duals and Densecharger

FallenPhoenix · Jun 1, 2004

ShadowGT said:
87, 89 or 91-93 all run about the same in my GT...actually it runs best with 89 or 87.

My wife's '00 V6 Stang pings badly with anything under 89. Only mods are duals and Densecharger

Maybe from a lean condition? It would be interesting to see what it showed on a dyno A/F ratio.

8cyl · Jun 1, 2004

RTFM!!!

DerekStangGT · Jun 2, 2004

ok, newb question here. what exactly is 1) pinging, 2) knocking, and 3) detonation, and how can i tell when any of these are happening??

FallenPhoenix · Jun 2, 2004

It's when the air/fuel mixture explodes before it should and basically pushes the piston the wrong way, which if you can imagine what's actually happening in the engine, is a very very bad thing. Many things can cause pinging but it's basically when the cylinder is too hot and ignites the mixture without the spark plugs assistance. Deposits in the cylinder, high intake temperatures and a dangerously lean condition can all spell disaster for your motor.

DerekStangGT · Jun 2, 2004

FallenPhoenix said:
It's when the air/fuel mixture explodes before it should and basically pushes the piston the wrong way, which if you can imagine what's actually happening in the engine, is a very very bad thing. Many things can cause pinging but it's basically when the cylinder is too hot and ignites the mixture without the spark plugs assistance. Deposits in the cylinder, high intake temperatures and a dangerously lean condition can all spell disaster for your motor.

so how can i tell if im pinging? what does it sound like?

mcmmotorsports · Jun 15, 2004

DerekStangGT said:
so how can i tell if im pinging? what does it sound like?

It sounds like little ball bearings bouncing around in your valve covers.

BMan5150 · Jun 15, 2004

Fact: Unless your car suffers from spark knock/detonates/pings on 87 OR you are running a higher base timing (timing adjuster) OR a chip with advanced timing tables, 87 is the way to go and you are wasting your money spending extra on higher octane.

Fact: According to Ford's own repair/diagnosis manual on the 4.6L Stangs, base timing from the factory (bone stock) can vary by as much as 2 degrees. This means some stangs come from the factory with a base timing of 8 degrees and some come from the factory with 12 degrees BT.

Fact: From the day I bought it (stock) up until today (minor bolt-on mods), my car pings on 87, 89, and even a little on 91 octane. 92-93, I get no throttle tip-in ping or detonation at 3500-4800 RPM @ WOT.

Fact: I use at least 92 octane in my stang to prevent detonation.

Fact: The amount of energy in 87 octane verses 93 octane is generally the same (all other things being equal.)

Fact: My car does not make more power on 92 octane.

Fact: My car does not make less power on 87 octane.

Fact: Octane is only a measure of fuel's resistance to pre-ignite. In other words, higher octane will help reduce the chance of the air/fuel mixture being ignited by anything other than the spark from the plug. Other things that ignite the air/fuel prematurely and cause spark knock/detonation - excessive cylinder pressure (boost), hot spots on pistons due to carbon buildup.)

Carry on . . .

Slapyo · Jun 16, 2004

i run 91 in my stang cause i put the timing adjuster on, but also i would say it's just outta habit too cause i filled it with 91 before i had the timing adjuster.

Bruno Rodrigues · Aug 2, 2018

Ok I own a 2000 mustang GT with simple bolt ons, I have a diablo sport I2 tuner and it has the 87 street tune, 91 sport tune and the 93 race tune. I know these cars run perfectly on 87 octane when stock or nearly stock but I’m not sure which tune to install as the 93 racing tune is supposed to deliver more power but does it actually since these engines run optimum on 87 octane? Can I install the 93 race tune and still continue using 87 octane? I only have CAI, throttle body spacer, exhaust (stock headers) and 3.73 gears.

Mustang5L5 · Aug 7, 2018

Bruno Rodrigues said:
Ok I own a 2000 mustang GT with simple bolt ons, I have a diablo sport I2 tuner and it has the 87 street tune, 91 sport tune and the 93 race tune. I know these cars run perfectly on 87 octane when stock or nearly stock but I’m not sure which tune to install as the 93 racing tune is supposed to deliver more power but does it actually since these engines run optimum on 87 octane? Can I install the 93 race tune and still continue using 87 octane? I only have CAI, throttle body spacer, exhaust (stock headers) and 3.73 gears.

The tunes change timing curves in the ECU. Timing is one variable that can cause detonation with lower octanes but changing timing can increase power. With aggressive timing curves, you need the higher octane.

So if you plan on running the 93 race tune, you should fill your tank with 93, run it down and then top it off again with 93 and then install the tune.

Bruno Rodrigues · Aug 7, 2018

Mustang5L5 said:
The tunes change timing curves in the ECU. Timing is one variable that can cause detonation with lower octanes but changing timing can increase power. With aggressive timing curves, you need the higher octane.

So if you plan on running the 93 race tune, you should fill your tank with 93, run it down and then top it off again with 93 and then install the tune.[/QUOT

Ok so it is ok to run the 93 race tune on an engine that’s built to use 87 octane? Cause these engines only have 9:1 compression to begin with

What octane to run on 4.6 GT Anyway?

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